My pet peeve is arrogant writers. People who think that because they know how to use a semicolon and can churn out a couple of pages of content per post that they're writing has more objective value than someone who doesn't write the same way or the same length. People who try to gatekeep because they think that a certain kind of roleplay is inherently less complex or less intricate or even less aesthetically interesting than another kind. Those who callously refuse to empathize with less experienced players/gms like they were born with a pen and a pad in the womb. People who talk down to other writers and roleplayers because they aren't as nerdy as they are. It manifests itself in so many different forms. But arrogant writers are the worst.